Cosmology with torsion: An alternative to cosmic inflation

TL;DR

This paper presents a cosmological model based on Einstein-Cartan gravity where spacetime torsion prevents singularities and naturally solves flatness and horizon problems without inflation, proposing a universe bounce possibly linked to black hole dynamics.

Contribution

It introduces a torsion-based cosmological scenario that explains universe flatness and homogeneity without inflation, connecting black hole physics to the Big Bang origin.

Findings

Torsion prevents the initial singularity, leading to a finite minimum universe radius.

The model naturally solves flatness and horizon problems with a tiny negative torsion density.

Proposes a universe bounce linked to black hole interior dynamics.

Abstract

We propose a simple scenario which explains why our Universe appears spatially flat, homogeneous and isotropic. We use the Einstein-Cartan-Kibble-Sciama (ECKS) theory of gravity which naturally extends general relativity to include the spin of matter. The torsion of spacetime generates gravitational repulsion in the early Universe filled with quarks and leptons, preventing the cosmological singularity: the Universe expands from a state of minimum but finite radius. We show that the dynamics of the closed Universe immediately after this state naturally solves the flatness and horizon problems in cosmology because of an extremely small and negative torsion density parameter, $\Omega_S \approx -10^{-69}$. Thus the ECKS gravity provides a compelling alternative to speculative mechanisms of standard cosmic inflation. This scenario also suggests that the contraction of our Universe preceding the bounce at the minimum radius may correspond to the dynamics of matter inside a collapsing black hole existing in another universe, which could explain the origin of the Big Bang.